You youngsters with your new-fangled automatic things are probably bored
with this discussion of old new technology. Just hit delete.
A 'fluid drive' transmission is where you have a fluid
coupling backed by a conventional clutch and a conventional three speed
transmission.
Technically there's no such thing as a "fluid drive transmission."
The Fluid Drive is the coupling between the engine and transmission. Fluid
Drive was available in front of a three speed or a semi-automatic.
Fluid-Torque Drive was a torque converter introduced about 1952.
The Prestomatic/Gyromatic/Whatever-matics (semi-automatics)
had the same fluid coupling and conventional clutch backed by a four-speed
manual transmission with two ranges - low and high. Each range could be
shifted up or down one gear by a solenoid.
The M-6 semi-automatic is a four speed, but not manual; it's a
hydraulically controlled planetary gear system with a unique countershaft
cluster. Upshifts are controlled within a range [low or high] by the
accelerator in conjunction with the hydraulic system [vacuum on prewar cars] and
downshifts [passing gear] by means of an electrical kickdown switch.
An interrputer switch momentarily kills the ignition to reverse torque when
coming to a stop so that the transmission will downshift. [This is
a simplified explanation.]
The driving torus of the Fluid Drive is mounted on the flywheel. The
clutch is mounted on the driven torus member of the Fluid Drive, not on the
flywheel.
--Roger van Hoy, '55 DeSoto, '58 DeSoto, '42 DeSoto, '66 Plymouth, '81
Imperial, Washougal, WA
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